Recent progress in explosive technology has been in the area of cast-cured, plastic bonded explosives (PBX). Explosives development efforts have produced a number of successful rubbery energetic PBX compositions. These PBX compositions demonstrate better safety and vulnerability characteristics than TNT-based melt-cast compositions. There is, however, an increasing need to significantly improve the performance of PBX materials, particularly for specific types of warhead applications. Currently, energetic but sensitive explosive materials are used in high performance shaped-charge weapon systems. Much concern has been raised over the ability of these sensitive explosives, when used in weapon systems, to meet insensitive munitions requirements. Typical plastic-bonded explosives contain binders of inert polymers. While the inert binders desensitize the hazardous explosive solid ingredient with which they are mixed, they also diminish or degrade the useful explosive energy. When inert polymers are replaced by energetic polymers in the composition, performance is enhanced due to the additional chemical energy provided by these energetic polymers. As the energetic binder content is increased, the tetranitramine level of crystalline explosive filler such as cyclotetramethylene tetranitramine (HMX) is reduced. The resulting transfer of energy releasing groups from the solid phase to the soft polymeric binder phase results in a more favorable tradeoff between performance and hazard properties than now exists with conventional PBX's using inert polymers.
Considerable effort has been expended in developing energetic polymers Among the recent successes in development of energetic polymers for binder application is glycidal azide polymer (GAP).
GAP is an energetic polymer which is essentially a honey-like, pourable, viscous material. It requires a liquid plasticizer to reduce its viscosity to achieve the high solids loading required for energetic compositions. Insensitive high explosive formulations containing GAP, HMX and a single plasticizer are known. For example, trimethylolethane trinitrate (TMETN) a friction sensitive energetic plasticizer has been used in GAP/HMX formulations which have an unfavorable embrittlement problem at low temperature (&lt;-20.degree. F.). These single plasticizer formulations are limited to about 70% to 75% by weight of explosive solids. Additionally, processing of single plasticizer formulations containing GAP and high weight percentages of solids is difficult because of the high viscosity and flow properties of GAP.